Net Real Estate and Secured Note Payable Balances for Each Segment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Net Real Estate	$ 1,664,555		$ 1,668,182
Secured Notes Payable	1,056,736	[1]	1,057,680	[1]
Total Retail
Segment Reporting Information [Line Items]
Net Real Estate	664,151		669,177
Secured Notes Payable	397,029	[1]	397,732	[1]
Total Office
Segment Reporting Information [Line Items]
Net Real Estate	762,210		759,203
Secured Notes Payable	427,953	[1]	428,194	[1]
Total Multifamily
Segment Reporting Information [Line Items]
Net Real Estate	36,020		36,391
Secured Notes Payable	101,444	[1]	101,444	[1]
Total Mixed-Use
Segment Reporting Information [Line Items]
Net Real Estate	202,174		203,411
Secured Notes Payable	$ 130,310	[1]	$ 130,310	[1]

[1] Excludes unamortized fair market value adjustments of $12.3 million and $13.0 million as of March 31, 2013 and December 31, 2012, respectively.